A bicycle frame includes a front part and a rear part. The front part includes head tube, a seat tube and a down tube connected between the head tube and the seat tube. A first connection portion is connected to the conjunction portion of the seat tube and the down tube. The rear part includes a second connection portion, a connection plate extending from a top end of the second connection portion, and two chain stays and two seat stays extending from the connection plate. The connection plate is fixed to the seat tube by at least one bolt, and the first and second connection portions are connected to each other by at least two bolts. The first connection portion includes a ridge which is engaged with the groove defined in the second connection portion.